文档介绍：Chapter 2
This chapter describes the basic features of all kinds of tissue cells, an important foundation for understanding physiology. These features include: 1. the structure of cell membrane and transport of substances through cell membrane; 2. electrical phenomena of the cells; transduction; 4. muscular contraction.
A mammalian cell membrane posed of two layers of lipid in which protein molecules are embedded. The position of the cell membrane acts as a barrier, which limits transmembrane movement for most of the molecules inside and outside of the cell. Some of the proteins in the cell membrane, however, form structures that permit transmembrane movement for certain water-soluble molecules. The cell membrane is therefore described as semipermeable, through which different kinds of substances pass across in different ways. Lipid-soluble molecules are capable of moving freely across the cell membrane by simple diffusion down their concentration gradients. Most of the molecules inside and outside of cells, however, cannot cross membrane without assistance. Two kinds of proteins in the cell membrane, called channels and carriers, provide permeability for these water-soluble substances, through which ions and glucose/amino acid can pass across membrane. Those two kinds of transmembrane movement are called facilitated diffusion. In some situations, the molecules pa